Electrochemical characterization of sulfur with low depth of charge/discharge in lithium sulfur batteries

• The charge/discharge electrochemical window of Li-S batteries is limited to a narrow range (1.95-2.45 V).
• In this narrow electrochemical window, the electrochemical reactions only occur in the liquid phase.
• This narrow electrochemical window provides improved capacity performance and cycling performance.

In this research, a narrow charge/discharge electrochemical window is enforced for lithium sulfur batteries. In this way, the active material of the electrode (which is sulfur in the initial state) is limited to Li2S8 and Li2S3, leading the electrochemical reactions to take place in the liquid phase and thereby improving the capacity performance and cycling performance. After 50 cycles at a current density of 0.1 mA cm−2, the specific capacity obtained using a narrow electrochemical window (1.95-2.45 V) (490 mAh g−1) was greater than that obtained using a wide electrochemical window (1.7-2.8 V) (435 mAh g−1). This finding demonstrates the feasibility of improving the electrochemical performance by employing a suitable electrochemical window to restrain the phase transformation to the middle liquid phase.